People(old and young) give away their entire life savings to scammers every day, everywhere in the world. You don't hear about it on the internet all the time because we either got used to it or they don't want the publicity. You hear about big cryptocurrency scams more often because people invested are more into tech and spend time on the internet. Do you say that cash is not ready or appropriate for mainstream use? What about that cashier that never has that 1c of change back? Clearly a sign of not being appropriate for mainstream.

Those generic arguments can be applied to literally everything we already have. People get scammed via their bank accounts every day too, people literally get scammed by the phone. You have to use your brain when it comes to _anything_ that involves a real world value these days, saying 'crypto bad cause scams' is pointless as there are way more scams involving real world money everywhere.